Warning: Please excuse my rudimentary test with the beer bottles.
I received this lens on Friday (2nd hand) and had a chance to shoot Saturday (briefly). Unfortunately I didn't have the tripod collar (arrived today) and had to hand hold. To make a long story short, all shots at F4.0 through F7.1 were 'muddy' and out of focus. Oops. I figured we had an issue with the lens, but at F8.0 it was sharp as a tack. So I was very confused, considering the shutter speed was getting shorter at F8.0. However, I figured I would wait to test with the tripod collar before making a snap judgments.
To today - with the tripod collar on the lens and the lens on the tripod, I tried some test shots. Surprisingly focus seemed OK. Based on my hand held test Saturday (maybe it was an anomaly), I thought for sure I had an extreme back focus issue and F8.0 allowed the subject to finally come in focus. Looking at the shots today, I think it is pretty close, maybe slightly off one way or the other, but very close. Based on reviews, I was expecting F4.0 to be very sharp. See the images below.
All shot DNG, A-Priority, ISO 250, +.3 EV (always on my K200D), 300mm on the tripod with 2 second timer, mirror lock up.
The closest Corona bottle is the focus point. Nothing done to these except resize.
F4.0, 1/125
F5.6, 1/60
F8.0, 1/30
F11.0, 1/15
Another weird thing... Every shot at F4.0 seems to be underexposed by 1/3 to 2/3 EV. Not as evident in these shots, but trust me, it is always the case.
Any thoughts on the under exposure or the focus?
Thank you!
Last edited by joeyc; 08-31-2009 at 08:47 PM.